The invention concerns a safety switch pursuant to the preamble of claim 1.
Safety switches of this type are used in the area of safety technology, with said switches being used, in particular, for monitoring hazardous areas around machines and systems.
The safety switch generates a switching signal that corresponds to the monitoring function of the switch, and the signal is sent to a controller used, e.g. for controlling a machine that is to be monitored. If the safety switch detects a non-hazardous state, in particular, that a door to be monitored is closed, a switching signal having the “switched-on” switching state, corresponding to an active safety condition, i.e. a release signal, will be generated. If the controller receives this release signal from the safety switch, the controller can start the operation of the machine, or allow the machine to continue to operate. If, however, the safety switch detects a hazardous state, e.g. an open door, the safety switch will generate a switching signal having the “switched-off” switching state, corresponding to a non-active safety condition. In this case, the controller will switch the machine off in order to prevent hazardous conditions.
Known safety switches have a reading head and an actuator that is movable relative to the reading head, with a transponder being provided on the actuator. For the case that the safety switch is used to monitor a door, in particular a safety door serving as access to a hazardous area, the actuator will typically be arranged on the door. The reading head will then be located on a frame surrounding the door. With a safety switch that is thus embodied, a switching signal will be generated that corresponds to a non-hazardous state if the reading head receives encoded signals generated by the transponder. In the case of a door monitoring system, this will be the case when the door is closed and the transponder consequently is located at a small distance from the reading head. In addition, a safety switch embodied in such a manner is used to generate a switching signal corresponding to a hazardous state if the reading head does not receive any signals from the transponder. For a door monitoring system this will be the case if the door is open and the transponder is consequently located at a large distance from the reading head.